Temperature calibrated metal vapor discharge lamp



R. w. SAMER 2,532,463

TEMPERATURE CALIBRATED METAL VAPOR DISCHARGE LAMP Dec. 5, 1950 3Sheets-S'neet 1 Filed March 23, 1949 IN VEN TOR.

RUDOL W. SAMER OQNEY TEMPERATURE CALIBRATED METAL VAPOR DISCHARGE LAMPFiled March 23, 1949 R. W. SAMER Dec. 5, 1950 5 Sheets-Sheet 2 RUDOLF w.SAMER 8% A TTO/?NEY R. w. SAMER 2,532,463

TEMPERATURE CALIBRATED METAL VAPOR DISCHARG LAMP Dec. 5, 1950 3Sheets-Sheet 3 Filed March 23, 1949 f lr lll INVENTOR. RUDOLF W. SAMERTTOQNEY Patented Dec. 5, 1950 UNITED STATES PATENT OFFICE TEMPERATURECALIBRATED METAL VAPOR DISCHARGE LAMP Rudolf W. Samer, Elizabeth, N. J.,assignor to Hanovia Chemical and Manufacturing Company, Newark, N. J., acorporaticn of New Jersey Application March 23, 1949, Serial No. 83,004

1 4 Claims.

The present invention deals with a metal vapor discharge lamp and moreparticularly with a temperature calibrated metal vapor discharge larnp.

The intensity of radiation obtained from a metal vapor discherge lamp isdependent, among other factors, upon the temperature at which the larnpis operated. Ordinarily, for operation in some medium, such as air or aliquid, metal vapor discharge lamps are designed to give a peak outputat a specific ambient temperature. Where it is desirecl to keep the lampoutput substantially constant, for example in regard to photochemicalreactions or bactericidal effects, even while operation in ambienttemperatures which differ appreeiahly from the temperature for which thelamp was designed, the lamp is usually provided with a heat insulatingmeans which may he in the form of a light transrnissive jacket havingappropriate light transmission characteristics. such a jacket, however,absorbs some of the available light output of the lamp, for instance asmuch as approximately sixty percent (50%) of the ultraviolet radiationsand twenty percent (20%) of the visible radiatiohs may be ahsorhed.Maintaining a peak intensity of radiation by such known means isdisadvantageous nct only because oi the loss of output efliciency butalso in view of the limited heat insulation possible under changingtemperatures. For example, although a heat insulating means isadvantageous to the extent that it enables a lamp to operate under agreater ambient temperature range, the mere addition of the jacketintroduces a less of about twenty percent (20%) and more of theradiation due to absorption by the jacket, hence, with a constant powerinput the available radiation can not exceed about eighty peroent (89%)of the cptiznum value for the unjacketed lamp.

It is an object of this invention to provide a metal vapor dischargelamp adapted to give suhstantially uniforin peak intensity under Variousambient temperature& It is another object of this invention to provide ametal vapor discharge larnp adjustable to temperature changes. It is afurther object of this invention to provide metal vapor discharge lanpwhich can he adjusted at will or automatically to give the same pearl:intensity at constant power input for any selected ambient temperaturewithin a specified range of temperatures. Other objects and ad vantagesoi the present invention Will be apparent from the following descriptionand the accompanying drawings in which:

Figure 1 schematically illustrates one View of a metal vapor dischargelamp in bi-laterally symmetrical aspect,

Figure 2 schematically illustrates another view of a metal vapordischarge lamp taken at right angles to Figure 1,

Figure 3 graphically illustrates a section of a temperature calibratedmetal vapor discharge lamp,

Figure 4 schematically illustrates another ernhodiment of the presentinvention,

Figure 5 illustrates a front view of the apparatus of the invention, and

Figure 6 illustrates a cross-sectional view of the apparatus of theinvention.

The present invention provides an efcient metal vapor diseharge lamp foruse, for example, as a germicidal lamp in refrigerators, particularly ofthe type known as show case or reach-in." In such refrigerators, thefrequently handled contents are subject to bacterial infection andbactericidal lamps have been resorted to in order to preventcontamination. I have provided a hactericidal metal vapor discharge lampwhich is superior to bactericidal lamps heretofore known in that theintensity of radiation remains at its peak or optimum value regardlessof temperature changes. Thus, in cases where a lowering of thetemperature in a refrigerator would ordinarly so affect the operation ofa conventional lamp that its bactericidal efiiciency is substantiallyreduced, the larnp of the present invention maintains the desiresioptimun ultraviolet radiation and, consequently, a coinparatively highbactericidal efcieney.

According to Figure 1, the lamp oi the present invention comprisesessentially a glass envelope i of suitable transmission characteristicsprovided With an evacuation and filling tube 2 through which appropriategases, e. g. argon or neon, and a low melting point vaporizable metal 3,e. g. mercury, may be admitted. The four lead-in wires serve as supportsfor two electrodes 5, for example, coil coiled tungsten activated withalkaline earth metals or oxides or other suitable activation material,in such a mauner that each pair of lead-in wires on either side of thefilling tube form a continuous and independent electrical circuitthrough the electrodes in their respective sides of the envelope, asmore particularly illustrated in Figure 2.

The lamp is operated With the dome-shaped end in a lower position thanthe end containing the lead-in wires. Thus, if the lamp axis LL ismaintained vertical, the mercury 3 will roll to in space located in theplane of the electrodes and half way between the centers of theelectrodes. The true position of A in an actual lamp is dependent uponthe individual design, geom etry and physical and Chemical propertiesoff 'the Component parts. For example, a lamp may be constructed to haveone or more electrodes ;of suitable form depending upon whether 'thelampis a high or low pressure lamp and point A may be established inaccordance therewith.

For illustrative purposes with :respect to the position of A as shown inFigure 2, the distance AB corresponds to the proper spacing that isnecessary for optimum output of the desired radiation when the lamp isoperated in a medium, such as air, at an ambient temp raturecorresponding to the upper limit of the calibration range for the lamp.Similarly, the distance AC corresponds to the proper spacing that isnecessary for optimum output of the same radiation when the lamp is,operated in the same medium at an ambient temperature corresponding tothe lower limit of the calibration range for the lamp.

Figure 3 illustrates a graphic representation of a section of acalibrated metal vapor `discharge lamp as drawn to scale from ,an actuallamp. In ,this particular calibration, the temperature range is from 36F. to 70 F. and point A is located in space halfway 'between the Centersof two coil diseharge areas of which one such discharge area is shown.Both discharge ,areas and point A are in the same plane and thedischarge areas are so located that ,they are in the same relativeposition With regard to their individual coils. The lower 'limit of thecalibration range, e. g. 30 F., 'is so located with respect to th arcportion of the glass envelope that ,it is nearest to 'point A ,while theupper limit of the calibration range,

e. g 70 F., is farthest from point A. The spacing ;between point A and apoint on the glass envelope is determined by the proper spacing that isnecessary for optimum output of the same radiation over .the calibratedtemperature range. The temperature points on the glassenvelope, althoughthe distanees from point A to ,the temperature points ,are critical, maybe separated from each other by a distance depending upon the shap andsize of the bottom or arced .por tion of the glass envelope.

With the axis LL vertical, as shown in Figures 1 and2, .and the lampOperating in a medium at an ambient ,temperatur corresponding to the upr temperature calibration limit, the rate of evaporation of thevaporizab-le metal, for example mercury, is just snoient to maintain the,lamp wall at optimum Operating temperature'due to the heat transfer tothe envelope wall by the mercury vapor as it condenses on the wall androlls ,back down to the lowest point in the lamp. However, ii th ambienttemperature outside the lamp i lowered, then the temperaturedifierential ,between the envelope and the outside surrounding medium isincreased and, as a result, the rate of heat transfer away from theenvelope to the outside surrounding medium is increased and the envelopetemperature will be lowered unt-il a new condition of equilibrium existswhere the rate of heat transfer away from the envelope equals the rateof heat transfer to the envelope.

This corresponding lower envelope temperature is now lower than theoptimum temperature for the production of the desired radiation, and inconventional lamps the efiiciency drops In the lamp of the presentinvention, the shape of the envelope is such that as 'the lamp aXis LLis tilted away from the vertical, the liquid metal, e. g.

mercury, rolls along the envelope wall from point `B towards point C,hence, the distance between the 'mercury 'drop and point A becomesprogressively shorter. In this manner, the rate of evap- Qration ofmercury isregulated and, consequently, 'the .rate of heat transfer tothe envelope wall increases. If theilamp is tilted to the proper angle,the mercury drop .will come to rest at such point where its increased orregulated rate of evaporation and the -consequent increased rate of heattransfer to the envelope Will just compensate for the increased rate ofheat transfer away from the envelope occasioned ,by the aforementioneddrop in ambient temperature, and the net result is that 'the lamp will,with a constant .power input, continue Operating with'the optimumenvelope temperatureand optimum output of the desired radiation .at anyambient temperature within a specified range of 'temperatures The lamp'may be fitted with a standard four prong base. Thus, it `can be pluggedinto a standardzfourprong tube socket.

Temperature caiibration may be achieved, among other methods, bymounting th lamp in a holding device which will permit angulardisplacenent of the lamp axis LL relative to some arbitrarily chosenfixed reference place in the holding device or to the earths surface.The amount of .dispiacement is measnred by the relative motion betweenan index or pointer and a numbered scale, .one of which is fixed in.position while the other moves with the lamp axis 'the displacement ofwhich may correspond to the positions of Li, L2, LB, ,LG or L5 of Figure'3. The scale may be marked directly in terms of temperature.

Figure 4 illustrates another embodiment of the present invention withrespect to a preferred type of envelope Construction.

With reference to Figures 1 and .2, although the glass envelope may beadequate it has the disadvantage that over a prolonged period of timethe condensed mercury vapor may become partially permanently depositedalong the envelope wall farthest removed from the lamp filaments. TheConstruction of the envelope of Figure 4 is such that a substantiallylarge portion of the glass envelope is domashaped and lies below theelectrodes and is suitable for calibration according to the invention,while the portion of the envelope wall above the filaments issubstantially near the filaments and shaped to ,allow free flow of thecondensed mercnry vapor to the lower portion of the glass envelope. Inthis case, even though impcrfections in the smcothness of the glassenvelope may act to retard the flow of the condensed mercury vapor tothe lower portion of the envelope, the heat 'from the filaments acts to'limit undesired condensation of mercury above the electrodes andthereby insures a proper amount of vaporizable metal for the efcientoperation of the lamp. To further insure the availability of a properamount of vaporizable metal when the rate of vaporization issubstantially high, an excess of vaporizable metal is always present inan amount sunicient for eicient operation of the lamp so that at alltimes there is at least some metal in un- Vaporized form.

Figures 5 and 6 illustrate the complete apparatus of the invention Withemphasis on the automatic tilting mechanism for the temperaturecalibrated metal vapor discharge lamp.

In Figure 6, the protective housing 6 has mounted therein a thermalspring l wound in the shape of a spiral as shown in Figure 5. Theoutside end of the spiral is anchored around an anchor pin 8 and theinside of the spiral is rigidly held in the slot 9 of the pivot shaftla. Spring clips l l prevent lateral displacement of the pivot shaftalong its aXis. The lamp bracket !2 is firmly attached to the pivotshaft so that the lamp bracket and pivot shaft revolve as one unit.

The principle of operation of this mechanism is based on the fact thatthe thermal spring will Wind itself tghter as it is heated, and Willunwind as it is cooled. This is the case when the thermal springconsists of a bimetallic strip having the metal of greater coefficientof expansion on the outside. If the spring were coiled with the metal ofgreater coefficient of expansion on the inside, the spring would windtighter upon cooling. Either type of spring may be used provided dueconsideration is given to the position of the lamp and to thecalibration of the unit.

Since the outer end of the spring is held in place by the anchor pin 8,the expansion and contraction of the spring due to temperature change istranslated into rotary motion and is imparted as such to the pivot shaftse.

The unit is properly calibrated when the spring imparts the properangular displacement to the pivot shaft as is required by the lamp foroptimum output of the desired radiation at any ambient temperaturewithin the calibration range of the lamp. Calibration may beaccomplished by control of the thermal properties of the spring inregard to its metallic composition and by the dimensions and position ofthe bimetallic strip, e. g. diameter, spacing, number of turns, andinitial orientation relative to the lamp axis.

Figures 5 and 6 are not intended as detailed designs, but merelyrepresent schematic illustrations showing one mode of operation of theapparatus by automatic control. The apparatus may have manuallycontrolled tilting means so that when the ambient temperature of themedium in which the lamp operates is below a designated temperaturerange, the lamp may be manually tilted to correspond to the readings ofa thermometer.

The invention is not limited to the specific illustrations anddescription herein set forth, but may be construed to include variousOperating means and functions within the true scope of the invention.

What I claim is:

l. A metal vapor discharge lamp for maintaining substantially uniformintensity under changing ambient temperatures, comprising a lighttransmissive glass envelope containing at least a normally liquidvaporizable metal and a pair of spaced electrodes, said envelope havingan inverted dome-shaped portion, the inner surface of said dome-shapedportion being concave, said electrodes being spaced from said innersurface so that the distance from a point between said electrodes to alocation at the vertex of said concave inner surface is greater than anyother distance from said point to any other location on said concaveinner surface, a rotatable mounting means for said lamp, said rotatablemounting means having a rotational axis perpendicular to a vertical linefrom said point to a location on the said inner surface of saiddome-shaped portion, said metal being clisplaceable along the said innersurface upon rotation of said mounting and the distance between saidpoint and said metal being thereby changeable for regulating the rate ofvaporization of said metal to maintain substantially uniiorm intensity.

2. A metal vapor discharge lamp for maintaining substantially uniformintensity under changing ambient temperatures, comprising a lighttransmissive glass envelope containing at least a normally liquidvaporizable metal and a pair of spaced electrodes, said envelope havingan inverted dome-shaped portion, the inner surface of said dome-shapedportion being concave, said electrocles being spaced from said innersurface so that the distance from a point between said electrodes to alocation at the vertex of said concave inner surface is greater than anyother distance from said point to any other loca tion on said concaveinner surface, said locations on said inner surface being temperaturecalibrated locations, a rotatable mounting means for said lamp, saidrotatable mounting means having a rotational axis perpendicular to avertical line from said point to a location on the said inner surface ofsaid done-shaped portion, said metal being displaceable along saidcalibrated inner surface upon rotation of said mounting and the distancebetween said point and said metal being thereby changeable forregulating the rate of vaporization of said metal to maintainsubstantially uniform intensity under changing ambient temperatures.

3. A metal vapor discharge lamp according to claim 1 wherein saidvaporizable metal is mercury.

4. A metal vapor discharge lamp according to claim 1, comprising meansfor automatically rotating said rotatable mounting in accordance withchanging ambient temperatures, said auto matic means comprising atemperature sensitive bimetallic thermal spring connected to a pivotshaft having an axis corresponding to said rotational axis.

RUDOLF W. SAMER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS' Number Name Date 950,'709 Thomas Mar. 1, 191010063166 Ludwig July 2, 1935 2,110,603 Knowles Mar. 8, 1938 2,326346Foote Aug. 10, 1943

